Apparatus for kiln-drying lumber and other substances



7, 1924 4 Sheets-Sheet l J F. COBB APPARATUS FOR KILN DRYING LUMBER AND OTHER SUBSTANCES Filed Oct.

Oct. 14, 1930. J F. COBB 1,778,586

APPARATUS FOR KILN DRYING LUMBER AND OTHER SUBSTANCES Syvum/Hoz;

Oct. 14, 1930. J F. COBB 1,778,586

APPARATUS FOR KILN DRYING LUMBER AND OTHER SUBSTANCES oct. 14, 1930. J F, COBB 1,778,586

APPARATUS FOR KILN DRYING LUMBER AND OTHE SUBSTANCES .substances exhibited in like mannerto :the

operation upon .it .of the circulatory drying` Patented Oct. 14, 1930 UNITED 4STATE s PATENT-OFFICE J rORREsT conn, OF PORTLAND; OREGON',- AssieNOR rrO MOORE DRY RILN COMPANY,

. A oORrORATiON-OR FLORIDA i APPARATUS FOR Kinn-DRYING LUMBER Ann OTHER sUBs'rANcEs.

appuuationfued october ',","`19:a4..l serial No- 742,190."4 Y

My invention relates to improvements yin method and apparatus forl drying .different substances, but particularly lumber, through the applicationwithin a kiln of a circulatoryV gaseous drying medium either with out the use of artificialheat.

of mechanical em odiment, it is necessary to take into account the fact that the circulatory medium takes up the comparatively heavy vapor which green wood, for example, gives off, and therefore an important feature ofmy invention consists in providing ascending and descending currents of the circulatory medium with minimum obstruction and without conflicting movement of the ascending, and descending columns, respectively. By this means not only is a constant circulation pro` vided, but a maximum degree-of acceleration of the circulatory movementis effected, by aid of which the best results are obtained in the shortest period of time, and with equal distribution of the drying medium into effective contact with all parts of the drying stock exposed to it. l

My present invention is applicable particularly to the drying of flat-piled lumber as contradistinguished from'edgefpiled lumber, and is specially adapted to meet-the requirements of such piling vof lumber'orfof other medium.

My invention, within thescope above indicated, inall forms of its mechanical embodiment, comprehendsa kiln. One form of embodiment is thatin which the circulation of the gaseous drying medium is elfectedwholl` through the application r.the/reto fof heat, by; the variation of the density of thecilrcujlating medium. This may be vconveniently designated a ysystem of natural circulation. Another form of embodiment is thatin which the circulation is prodticed partly by means of heat and partly by the aid of mechanical that in which the means employed of promot- Ying circulationis entirely mechanical, yandin which such heat as it may be desirable to employ may be provided Wholly or substantially -ventionmay either'be inferred from the forec .y -fgoingjvgeneral description or will be obvious In respect to m. invention andinany formi..

9T with? clusively are employed.

.form of fan attachment Which is an example Still another form of embodiment is onthe outside ofthe kiln with which, and withithe source of heat also, said mechanical means is in operative communication. p1=Vhatfgare thevarious objects of vmy in-l a kiln constituting one form of embodiment offmy invention in its mechanical aspect, wherein are provided means for eiecting natural circulation as aforesaid.

`Figure II is a `similar viewjofakiln in a modified form of embodiment of my invention in its mechanical aspect, showing a kiln op- ,erative partlyA by natural` "circulation and partly by auxiliary mechanical means.

Figure III is a similar view of a kiln in a' furthermodiied'k form,l of` my invention in which inecha-nicalmeans of circulation ex- FigureIVisa longitudinal vertical section taken ason theline IV--IVv of Figure I.

Figure v.V is a view similar to Figure IV taken as on the line vV-V of Figure II.

Figure VI is a partial view similar to Figure IVtaken on the line VI-VI of Figure III; i

.Figure VII is a perspective view of one of mechanical circulation means applicable to either of the kilns shown in Figures .II or' IIL;

Referring to the numerals on the drawings,

1 .indicates the side walls, 2 the top, and 3 the 90 'bottom wall, which are united one to another to form a kiln-chamber of that general type in which the lmaterial to be dried is, upon suitable conveyors, introduced at one end of the kiln, and is withdrawn from it at the otheriend. The kiln-chamber is provided, as usual, with end doors, not necessary to illustrate, which areopened for the passage of loaded conveyors into and out of the kiln 10u as occasion requires, and which are kept closed while the kiln is in operation.

The kiln may be of any suitable and preferred design and dimensions, and may be made of any suitable preferred material that is adequately ircproof, the kiln shown in the drawings being made of concrete by way of preferred example.

At any desired and convenient height above the bottom wall 3, I prefer to provide a succession, at suitable intervals, of cross-beams 4 which consist of iron I-bcams. The beams 4 are examples only of any suitable means of support for the material to be dried, and to that end preferably carry parallel rails 5 and G to constitute a track extending through the kiln from end to end. Said rails are designed and adapted to accommodate conveyors or wheeled trucks 7 which are preferably united in pairs as by a bunk 8 upon which the drying stock 9 is piled in substantially horizontal layers. rIhe stock 9 is represented in the drawings by boards that are laid flat side down upon the bunks 8 and are built up in vertically successive layers with non-intercommunicating spaces 10 between. Said spaces may be provided by the introduction between layers of cross piling strips, not illustrated, so that they may serve to separate the successive layers of the stock without obstruction of the spaces 10 which the strips define between said layers.

The drying stock is stacked into two piles separated by a clear and unobstructed medially disposed vertical flue 11, which extends substantially from end tov end of the kiln and is deiined by the relative disposition of the piles. From the under side of the top 2, I prefer to provide upon opposite sides of the two drying stock piles battle 14 and 15. Said battles when used are preferably made of flexible material, such, for example, as canvas of suitable weivfht.

The length of the bunks 8, to which is restricted the width of the combined stock piles, is such as to provide space at their opposite ends sufficient to accommodate lateral flues 17 and 18 which, being in part defined by the piling of the stock, are disposed for the most part above the cross-beams 4, and extend substantially to the stop 2. The top may be furnished with the usual succession of ventilators 19, which are provided each with the usual damper 19, or other means of regulation.

Below the bunks 8, I provide rigid battleplates or walls 20 and 21 which extend substantially the full length of the kiln. They serve to divide the lower interior of the kilnchamber below the top of the bunks '8, or, in other words, the stock-supporting level, into three longitudinally disposed compartments, namely, lateral compartments 22 wlnch communicate directly with the iues 17 and 18, respectively, and an intermediate compartment 23 located vertically below the medial flue 11 and in direct communication therewith,

In Figure I, I show, for that form of embodimentof my invention, said lateral compartments as provided respectively, with a series of heating pipes 24 and 25 which constitute heating coils that are in operative connection with a source of heat, not illustrated. The pipes 24 and 25 may be supported in position by any suitable means, for example by pipe hangers 26 and horizontal supports 27. Above each heating coil or set of pipes 24 or 25, I prefer to provide a pipe 28 that is in operative communication with a source of Huid supply, not illustrated, and which is adapted to discharge through a series of upwardly directing vents, steam, water under pressure, or compressed air, according to preference. The function of said pipe 28 is that of auxiliaries to promote upward movement of thev circulatory medium through the lines 17 and 18, respectively, and also to impart thereto moisture, when required for humidifying effect. A downwardly discharging pipe 29 is preferably used in operative con- `junction with the pipes 28.

The space defined between the balles 20 and 21 constitutes a reservoir of capacity to amply accommodate any accumulation which may occur of the circulatory medium in a moisture laden state, and thereby to* remove from contact with the piles of drying stock any excess moisture which the operation of the circulation may extract from the stock in the process of drying it.

I prefer also to provide in the kiln shown in Figure I a fresh air duct 30 which extends preferably from end to end of the kiln, and which affords means of supply, that may be regulated at will, for the introduction of fresh air from the outside into the kiln. A grid 32 is preferably provided as a cover to the duct Within the kiln.

In the form of kiln illustrated in Figure I as described above, a constant movement of the circulatory medium is promoted, in the direction of the arrows shown in the figure, solely either by the application of heat derived from the pipes 24 and 25, or by variation of density in the gaseous drying medium, which may be effected simply by the drying of the stock. Such a means of promoting circulatory movement is all that is required for certain drying operations. The ascending columns of the circulatory medium which rise through the iues 17 and 18 are entirely unobstructed, and are driven with suflicient force by the buoyancy of the circulatory medium derived from the heat of the pipes 24 t l and 25, respectively, through the short spaces 10 provided between the successive layers of the drying stock piles. The movement of the said ascendingcolumns of the drying medium serves to prevent stagnation in any of the llO spaces 10, and :is aided by the downfall of the gaseous discharge from the flue 11 to keep a constant flow of the circulatory medium, hoW- ever heavily laden with moisture, into the medial Hue l1 through which it tends, by reason of its loss of heat, to drop by gravity into the reservoir defined between the baffle walls 20 and 21. By the sole means above described, a constant circulation and recirculation, having for many purposes an allefficient rate of movement of circulation, is produced.

Nevertheless, for the drying of some substances it may be necessary to providein conjunction with the pipes 24 and 25, aux'- iliary mechanical means for promoting circulation. The combination of the heating pipes with mechanical means of circulation is shown in Figure II, for example, in which the bottom wall 3 is surmounted by a floor 31 which is divided into longitudinally extended compartments 33, 34, and 35, by vertical partition walls 36 and 37. By means ofapertures 38 provided in the floor 31 at intervals along its length and above the several compartments, respectively, just named, provision is made for al constant circulation of the circulatory medium withdrawn fromthe interior of the kiln and afterwards 'returned thereto by means of suitable fan mechanism. For example of such mechanism there is shown, in Figure VII, a fan-case 39 provided with suitable apertured delivery-ducts 4() and 41 and an intermediate suction-duct 42. The chiots 40, 42, and 41, are designed to be, in effect, thrust longitudinally into the compartments 33, 34, and 35, respectively, so as to constitute the compartments 33 and 35 into separate air delivery compartments,A and the compartment 34 into aI suction compartment.

It will be. understood, of course, that the employment of the precise construction ot' fan mechanism shown in Figure VII is entirely optional vso far as the introduction of the ducts 40, 42, and 41 into the compartments 33, 34, and 35, is concerned, and that communication with said compartments may bqe made, if preferred, directly as by shortening the ducts last named to no more than their necks 43, 44, and 45; but this is a mere mechanical variation of detail.

In Figure II, the baffles, which may be of the same shape and construetion` as those shown at 20 and 21 in Figure I and which are for that reason designated by the same numerals, terminate above the top of the floor 31 so as to leave a space between the floor and the lower edges of said baffles, respectively.

rllhe effect of this construction is to provide means of induced circulation underneath the edges of the baffles, so that any tendency at any point of stagnation of the drying medium as, for example, in the reservoir defined between the bafles 20 and 21 may be entirely eliminated.

In Figure III, I show a form of embodiment of my invention in which an all mechanical means of circulation is substituted for the means of natural circulation shown in Figure I, or for the combined natural and mechanical means shown in Figure II. In that figure. vertical walls 46 and 47 springing from the bottom 3 of the kiln may be. with the effect of' balaplates, substituted for the battle-plates 20 and 21 heretofore described The walls 4G and 47 extend upwardly in .sulliciently close proximity to the bottom of' thc bunks 8, where they are preferably provided, respectively, with horizontal or other fiangcs 48 which extend, respectively, toward the side Walls 1 of the kiln, and terminating preferably in flange extensions 49, define restricted throats communicating. respectively, with the fiues 17 and 13. A horizontal cross-partition 50 extends substantially the entire length oi' the kiln between the walls 4G and 47, and defines above it the bottom of a reservoir,

equivalent in function to that already re ferred to as defined by the bafiles 2O and 21. The horizontal wall 5() is provided at intervals along its length with apertures 51, which afford operative con'nnunication between said reservoir and a suction return-duct 52 defined below it by the conjoined walls 3, 46, 5l) and 47.

Lateral delivery-ducts 53 and 54 are provvided between the walls 4G and 47 and the side Walls 1 adjacent thereto, respectively. rPhe ducts 52, 53, and 54. may be operatively conjoined to any suitable fan mechanism, such'for example` that shown in Figure VII.

In the form of embodiment of my invention shown in Figure III, means -for heating the circulatory drying medium may be provided outside of the Iiln proper by heating coils, not illustrated, in operative communication With thefancase 39. In this way all of the circulating medium may be heated, with the drying effect desired, by means loiated entirely or substantially outside of the iln.

The form of embodiment of my invention shown in Figure III is especially efficacious for the quick drying of green lumber or lumber in which is present large volume of Water, to effect the elimination of which, practical efiiciency in the operation of the kiln demands that there shall be no stagnation of the circulatory medium or.k slowing down of therate of circulation at any point throughout its course.

It should be observed that the length of the spaces 10 and provision for their discharge, respectively, into the capacious medial flue 11, contribute directly to the etliciency of my apparatus for the following reasons. The spaces 10 are each filled with a stratum of heavy fluid whose inertia tends in proportion to its volume to resist movement. That tendency of resistance to motion may be reduced by reduction of the transverse eX- tent of each stratum, so as to require comparativel)v little driving force in the circulating medium to compel clearance of all the 5 strata. delined by the respective spaces l0,

and to keep the gaseous contents of said spaces constantly precipitating into the flue ll, from whence its incorporation into the main body of the circulating medium is facilitated.

The principle of operation above described applies if. in respect to the apparatus indicated in Figure III, for example, the movement of the mechanical means of circulation he reversed, as it obviously may be, so as to convert the suction ductl 52 into a single delivery duct instead of two, and the delivery duets 53 and 54 into two suction ducts instead of one. During reversal of circulation, operation of the auxiliaries 28 and 29 is interrupted.

Further description of the operation of my machine than that. which is presented in the foregoing specification is deemed unnecessary in this specification addressed to one skilled in the art.

Vhat I claim is:

A drying-kiln comprising a kiln chamber defining-walls, and a stock-supporting track extending longitudinally through the kilnchamber, in combination with baiiie walls dividing the kiln-chamber below the stock-supporting walls into three longitudinally disposed compartments, two lateral and one intermediate, baliies extending below the roof of the kiln chamber substantially in line with the bellies first above named, means for produringcirculation of a gaseous medium downwardly through the intermediate corn- 4@ partment and upwardly through the lateral compartments, by aid of medial and lateral tlues formed, respectively, by the piling of stock in substantially horizontal closed layers spaced apart, one layer above another, and

4,5 carried upon the track, and ventilators in the root' of the kiln chamber communicating with the space delined between the baliles eX- tending below the roof. y

In testimony whereof, I have hereunto set 5o my hand.

J FORRES'I COBB. 

